Laminated porous/non-porous membranes

ABSTRACT

A unified laminate of layers of polymer is disclosed, the laminate consisting of a layer of microporous substrate and an ultrathin layer of polyphenylene oxide (PPO) with an ultrathin layer of organopolysiloxane-polycarbonate copolymer disposed therebetween. The organopolysiloxane-polycarbonate copolymer layer serves to join the outer two layers together and provide cushioning to compensate for minor surface imperfections in the substrate.

United States Patent [1 1 Browall et a1.

[ Apr. 1, 1975 1 1 LAMINATED POROUS/NON-POROUS MEMBRANES [73] Assignee:General Electric Company,

Schenectady, NY.

Filed: May 20, 1974 Appl. No.: 471,320

[52] US. Cl 161/160, 156/285, 161/183 [51] Int. Cl B32b 3/26, B32b 27/28[58] Field of Search 161/160, 183; 156/285 [56] References Cited UNITEDSTATES PATENTS 3.740.305 6/1973 Hoback ct a1. 161/183 PrimaryE.\'aminerWilliam .1. Van Balen Attorney, Agent, or Firm-Leo l Malossi;Joseph T. Cohen; Jerome C. Squillaro [57] ABSTRACT A unified laminate oflayers of polymer is disclosed, the laminate consisting of a layer ofmicroporous substrate and an ultrathin layer of polyphenylene oxide(PPO) with an ultrathin layer of organopolysiloxanepolycarbonatecopolymer disposed therebetween. The organopolysiloxane-polycarbonatecopolymer layer serves to join the outer two layers together and providecushioning to compensate for minor surface im perfections in thesubstrate.

3 Claims, No Drawings LAMINATED POROUS/NON-POROUS bonate units anddimethylsiloxane units; and b) blends MEMBRANES ofpoly-2,6-dimethylphenylene oxide (PPO) andorganopolysiloxaneolycarbonate copolymer (as described BACKGROUND OF THEINVENTION above, such cogolymer being described in U.S. Pat. No.

The preparation of ultrathin membranes from poly- 5 3,189,662 Vaughn,Jr., incorporated by reference). phenylene oxide (PPO) andorganopolysiloxane- Organopolysiloxane-polycarbonate copolymer inpolycarbonate copolymer is described in U.S. Pat. apwhich alternatingblocks of repeating bisphenol-A plication Ser. No. 356,514 Ward, filedMay 2, 1973 polycarbonate units and repeating dimethylsiloxane andassigned to the assignee of the instant application. units are presentcan be prepared following the teach- Pertinent description is found inthe Ward application ings of Vaughn above, the resulting materials beingalin Examples 1, 2 and 3. ternating, random, block polymers of theABABA- The preparation of microporous polycarbonate resin yp in hich theblOCkS are polydispersez Si -C-O- :)C O EH CH I 3 s 3 rfi-l membranes isdescribed in U.S. Pat. application Ser. P l w ight average molec larweight lies in the N0- 569 Salemme, filed April 1974 and asrange of15,000 to 50,000, K and in being selected to signed to the assignee ofthe instant in ention- BOth the accommodate these values. Individualfilm thicknesses Ward and Salemme patent applications are incorpo-(after desolvation) will range from about 250A to rated by reference.about 500A.

In order to handle ultrathin membranes and put them The preferredsolvent for the organopolysiloxaneto use, support therefor onmicroporous substrate mapolycarbonate copolymer i l,2,3-t i hl terialhaving desired strength and flexibility must be (TCP). The preferredsolvent system for the mixture of provided. PPO andorganopolysiloxane-polycarbonate copolymer is a mixture of equal volumesof 1,2,3- DESCRIPTION OF THE INVENTlON trichloropropane andl,l,2,2,-tetrachloroethane In the case of providing support forultrathin PPO (TCE).

films it has been found advantageous to provide an in- Removal of thefilm from the surface of the filmformtermediate layer between the PPOfilm and micropoing solution as part of the laminate is most easilyacrous hacking materials such as Acropore AN-ZOO complished byvacuum-pickup as described in the (manufactured by Gelman InstrumentCompany) and Ward application. Apparatus for the film pickup in itspolycarbonate resin membranes prepared by the simplest form consists ofa closed chamber having one method set forth in the Salemme application.This inporous wall (e.g. sintered metal particles) at least thetcrmediate layer functions both as an adhesive and as size of the areaof film to be recovered. Initially a vaca cushion for the PPO layer tocompensate for minor uum is drawn on the chamber after the porous wallhas surface inperfections in the substrate. been covered with a layer ofthe microporous substrate The term layer as applied to PPO andorganopolysand the substrate is brought into contact with thedesoliloxane-polycarbonate copolymer materials refers to a vated film.The solidified film is pulled against the surunified lamina consistingofone or more ultrathin films face of the microporous substrate.Subsequent films of the given material in which the films are stronglymay be picked up in the same manner with each new bonded together, butneed not merge. film sticking to the earlier deposited one. Bubbles ofgas entrapped between films are no problem as long as j g s ggg igi ggfgg AND the vacuum is pulled, as the gas is gradually withdrawn from thebubbles by permeation and the film adjusts it- The ultrathin non-porousmembranes for use in the lf, h i ki as h gas leaves practice of thisinvention are prepared by the Ward Aty ieal a ri l ti f rhorganopolyslloxaneprocess by casting on a confined liquid surface. Apair polycarbonate l hi fil i 2-4% b i h f of movablelongitudinally-extending barriers initiallyarropolysiloxarrepolyearbonare SiO (CH 20 spaced apart a small distanceand in contact with the SiO(CH units per block] copolymer i TCP, A iliquid surface are employed, first, to accommodate the l Casting l i foh PPO l hi fil i 2 4% casting solution thcrebetween and second byrelative 60 by weight of polymer (PPO 20% by weight of the separationIhCI'COl it) COl'lil'OilZlbly permit spreading Of aforementionedrgancpo]ysiloxane-polycarbonate coihC CilSIlllg SOlUIlOll OVCI' thesurface OfthC film-support polymer) dissolved in equal quantities of andliquid. Water is the preferred film support liquid. TCE

Polymers of particular importance in the practice of P paration ofthecomposite PPO layer organopolysthis invention are those which a) includerepeating iloxane-polycarbonate copolymer layer nylonunits Comprisinghisphenol-A polycarbonate units and reinforced, polyvinylchlorideacrylonitrile copolymer dimethylsiloxane units and those whichinclude repeatlayer (Acropore), for example, is accomplished by apingunits in alternating blocks of bisphenol-A polycarplying a layer ofthemicroporous backing material over the porous wall of the pickup chamberwhile a vacuum is being drawn thereon and then bringing the substrateinto contact with a desolvated ultrathinorganopolysiloxane-polycarbonate copolymer film resting on the liquidcasting surface. In this way, the solidified film oforganopolysiloxane-polycarbonate copolymer is picked up and adheres tothe backing material. Multiple organopolysiloxane-polycarbonatecopolymer films may, if desired, be picked up in the same manner (vacuumbeing drawn in each instance) with each new film sticking to the earlierdeposited one. The thickness of the organopolysiloxane-polycarbonatecopolymer layer determines the extent of cushioning contributed by thelayer.

When the appropriate thickness (one or more films) oforganopolysiloxane-polycarbonate copolymer has been applied to themicroporous substrate, the film pickup procedure is repeated, preferablyadding two or more of the ultrathin PPO films to the aforementionedlaminate to produce the overall composite structure desired. Initially,ultrathin PPO membranes were ap-- plied directly to the Acropore, butdelamination occurred as is shown in Example 1.

EXAMPLE 1 Ultrathin PPO films were cast as required using a castingsolution containing 4% by weight of PFC 20% by weight oforganopolysiloxane-polycarbonate [60% SiO (CI-I 20 SiO(CH units perblock] copolymer dissolved in equal quantities of TCP and TCE. A sheetof Acropore was used as the backing and four ultrathin PPO films wereapplied in sequence to one face thereof using a vacuum chamber asdescribed herein. Tests were conducted on the laminate to determine theO /N separation factor thereof under high pressure (150-170 psig). Thesingle unified PPO layer separated from the Acropore backing in patches.It was concluded that this delamination was due to poor bonding betweenthe PPO and Acropore layers.

It was decided to attempt to improve this poor bonding condition and theconstruction of Example I was modified to introduce an intermediateultrathin layer of organopolysiloxane-polycarbonate copolymer.

EXAMPLE 2 A sheet of Acropore was applied to a vacuum chamber pickupsurface. First, an ultrathin film of 4% by weightorganopolysiloxane-polycarbonate copolymer a mixture of 5' parts [60%SiO(CH 4O SiO(CH units per block and 1 part [60% SiO(CI-I Si- O(CH unitsper block in TCP was picked up over the Acropore backing. Then insequence four ultrathin films of PFC (as in Example 1) were appliedthereover. This laminate was successfully tested for O /N separation athigh pressure (90 psig), the pressure application being cycled. Theenriched stream contained 44% by volume 0 and no delamination occurred.

Since the organopolysiloxane-polycarbonate copolymer layer is 10 timesmore permeable (in equal thickness) than the PPO membrane, the Oenrichment by the unified laminate is not significantly changed ascompared to the enrichment obtained with PPO in the absence of theorganopolysiloxane-polycarbonate copolymer layer. In the composite,however, the organopolysiloxane-polycarbonate layer overcomes' thedelamination problem by adhering both to the PPO layer and to theAcropore backing.

This general construction of Example 2 was repeated using microporousLexan (General Electric Company) polycarbonate (described in Example 3)and it was found that the layer of organopolysiloxanepolycarbonateprovided the desired cushioning and resistance to delamination.

EXAMPLE 3 A sheet of microporous polycarbonate was applied to thesuction surface of a vacuum-pickup chamber to serve as the backinglayer. An ultrathin organopolysiloxane-polycarbonate copolymer film asused in Example 2 was first applied to the backing layer. Next twoultra-' thin PPO films (as in Example 1) were applied over theorganopolysiloxane-polycarbonate layer. This composite was tested for O/N separation under vacuum with a pressure difference of 1 atmosphere.The test was successful, the enriched stream having 48% by volume 0 andno delamination occurring over an extended period of use.

The composites of this invention are intended for use as gas separationmembranes. For such applications the composites will usually besubjected to significant pressure differentials. In use, therefore, thecomposite will be supported on a series of cloth and fine screens.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

l. A composite containing unified layers of polymer consisting of anon-porous layer of polyphenyleneoxide/organopolysiloxane-polycarbonatecopolymer, a backing layer of a material selected from the groupconsisting of microporous polyvinyl chlorideacrylonitrile copolymer andmicroporous polycarbonate and an intermediate layer oforganopolysiloxanepolycarbonate copolymer adhering said non-porous layerto said backing layer.

2. The composite of claim 1 wherein the backing layer is microporouspolycarbonate.

3. The composite of claim 1 wherein the backing layer is microporouspolyvinyl chloride-acrylonitrile copolymer.

1. A COMPOSITE CONTAINING UNIFIED LYERS OF POLYMER CONISTING OF ANON-POROUS LAYER OF POLYPHENYLENEOXIDE/ORGANOPOLYSILOXANE-POLYCARBONATECOPOLYMER, A BACKING LAYER OF A MATERIAL SELECTED FROM THE GROUPCONSISTING OF MICROPOROUS POLYVINYL CHLORIDE-ACRYLONITRILE COPOLYMER ANDMICROPOROUS POLYCARBONATE AND AN INTERMEDIATE LAYER OFORGANOPOLYSILOXANE-POLYCARBONATE COPOLYMER ADHERING SAID NON-POROUSLAYER TO SAID BACKING LAYER.
 2. The composite of claim 1 wherein thebacking layer is microporous polycarbonate.
 3. The composite of claim 1wherein the backing layer is microporous polyvinylchloride-acryLonitrile copolymer.